Discard husks and stems from the tomatillos, and chop. Place the tomatillos and the next 8 ingredients (tomatillos through coriander) in a saucepan, and bring to a boil. Reduce heat, and simmer 1 hour or until mixture is thick, stirring occasionally. Spoon chutney into a bowl; cover and chill.
Prepare grill or broiler. Place grouper on grill rack or broiler pan coated with cooking spray; cook 6 minutes on each side or until fish flakes easily when tested with a fork. Serve with chutney; garnish with lemon, if desired.